Almost 700 years after black death has torn medieval Europe, scientists discovered a genetic mechanism that helped the plague kill tens of millions of people.
After the arrival of the disease in Great Britain in 1348, it is estimated that it wiped around half of the population, causing social, economic and cultural upheavals. Whole villages have disappeared, the shortages of labor have given surviving workers new negotiation powers and the rigid feudal system began to collapse.
The same pathogen has led recurring fatal waves of infections over the next 500 years.
New research shows how a single gene in Yersinia PestisThe bacteria that causes the plague, allowed it to last over the centuries, giving rise to a “slow continuous burn” – even after having already killed around 30 to 60 percent of the populations of Europe, Western Asia and Africa.
The study, led by scientists from McMaster University in Canada and the Institut Pasteur in France, analyzed hundreds of samples of victims of ancient and modern plague, focusing on a gene known as PLA, which allows Y.petis hide from the immune system.
The more copies of a plague of a plague, the more deadly it is – both for humans and for rats which are its main host.
Dozens of plague victims have been studied at a mass of mass burial in Thornton Abbey, near Immingham, in northern Lincolnshire
University of Sheffield / PA
The study, published in the journal Science, revealed that after the start of black death, Y.petis has evolved to have fewer copies of PLA. This reduced the mortality rate by around 20% and allowed infected hosts to live longer. In turn, this allowed the disease to propagate more.
A similar evolutionary change occurred after the plague of Justinian which devastated the Mediterranean in the 6th century, and was also seen in the modern strains of the plague, which continue to provoke cases in countries like Madagascar and the Democratic Republic of Congo.
A German drawing represents the ghosts of the victims of black death which were buried alive
Alam
The main impact of evolutionary change has been on rodents. Like the initial and more dangerous strains of Y.petis Killed a large number during black death, the populations of rats would have become dispersed in smaller and isolated groups.
In this new environment, softer strains of the plague – those that killed more slowly – had an advantage. They gave more time to the infected rats to move between these dispersed groups, further distributing the disease. Instead of exhausting, he continued his march at a slower and more sustained pace.
“It is important to remember that the plague was an epidemic of rats, which were the engines of epidemics and pandemics,” said Hendrik Poinar, of McMaster University, the main author of the study. “Humans were accidental victims.”
